<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 选择器样式 */
        div {
            background-color: red;
            width: 50px;
            height: 50px;
            line-height: 50px;
        }
        div:nth-child(2){
            background-color: blue;
        }
    </style>
</head>
<body>
    <div>88888</div>
    <div></div>
    <div></div>
</body>
</html>